a) Field of the Invention
The present invention relates to a fuel injection valve suitable for a fuel injection into an internal combustion engine of an automotive vehicle and a manufacturing method for a nozzle plate to be assembled into the fuel injection valve.
b) Description of the Related Art
A general fuel injection valve (normally called, fuel injector but also called fuel injection valve) used in an automotive engine includes a cylindrical valve casing having a fuel passage in its axial direction; a valve seat member having a valve seat and an injection outlet opening, the valve seat being disposed on an inner periphery of the valve casing at a tip end so as to enclose the injection outlet opening; a nozzle plate disposed at the tip of the valve casing so as to be faced against the injection outlet opening of the valve seat member and having a plurality of nozzle through-holes to inject fuel toward an external to the valve casing from the injection outlet opening; and a valve body to operatively be separated from the valve seat in response to an operation of an electromagnetic actuator installed within the fuel passage of the valve casing.
In such a kind of fuel injection valve as described above, the nozzle plate is formed by pressing a thin metallic plate and is attached onto the tip of the valve casing at a position so as to enclose the injection outlet opening of the valve seat member. In addition, a plurality of nozzle holes to inject fuel are penetrated through the nozzle plate.
A Japanese Patent Application First Publication No. Heisei 3-194163 published on Aug. 23, 1991 exemplifies a manufacturing process of the nozzle holes on the nozzle plate of the fuel injection valve.
A punching process is carried out for the nozzle plate using a punch so that the plurality of nozzle holes, each having a predetermined hole diameter and being inclined by a predetermined inclination angle with respect to a thickness direction of the nozzle plate and, therefore, a flow quantity of fuel and injection direction of the fuel injection valve can be determined.
During a valve opening of the valve body, the fuel supplied into the valve casing is injected from each nozzle hole toward an approximately intake port portion of the engine. At this time, the nozzle holes are so constructed that the fuel is injecting at a predetermined flow quantity according to their hole diameters and minute particles (granulations) of fuel can be achieved.
At a time of manufacturing the nozzle plate, the nozzle plate is punched in an opposite direction to the fuel injection direction of the fuel injection valve and the nozzle holes are opened on their front and rear surfaces. At this time, since one of the surface opening ends of the nozzle opening ends of fuel which is placed at outflow opening ends of fuel is an inlet side of the punch, a recess, viz., called a shear droop is formed in the vicinity to the outflow opening ends.
To avoid such manufacturing defects, the above-described previously proposed nozzle holes, a side surface which is placed at the outflow side of fuel from both surfaces of the nozzle plate is ground to scrape the shear droops placed in the vicinity to the nozzle holes.